1. Shedding light on Hexaquarks
Mikhail Bashkanov

2. Total cross section pn  d00
“d* resonance”
70 MeV 
NN*(1440)
P. Adlarson et. al Phys. Rev. Lett. 106:242302, 2011

3. 𝑑 ∗ (2380) dibaryon 𝚪 𝒅 ∗ =𝟕𝟎 𝐌𝐞𝐕≪ 𝚪 𝚫𝚫 =𝟐𝟒𝟎 𝑴𝒆𝑽 I(Jp) = 0(3+)
𝚪 𝒅 ∗ =𝟕𝟎 𝐌𝐞𝐕≪ 𝚪 𝚫𝚫 =𝟐𝟒𝟎 𝑴𝒆𝑽 u u u d d d
Threshold
I(Jp) = 0(3+)
80 MeV d* Δ Δ
𝑴 𝒅 ∗ =𝟐.𝟑𝟖 𝑮𝒆𝑽≈𝟐 𝑴 𝚫 −𝟖𝟎 𝑴𝒆𝑽

4. Dibaryon hadronic decays
PRL 106 (2011)
PLB 721 (2013) 229
WASA data
𝑑 𝜋 0 𝜋 0
𝑑 𝜋 + 𝜋 −
pn  d*(2380) 𝑝𝑛
𝑝𝑝 𝜋 − 𝜋 0
𝑝𝑛 𝜋 0 𝜋 0
𝑝𝑛 𝜋 + 𝜋 −
PRL 112 (2014)
PRC 90, (2014) d*
PRC 88 (2013)
PLB 743 (2015) 325 d* d*

5. 𝑑 ∗ (2380) decay branches 𝒅 ∗ decay channel Branching ratio, % 𝑝𝑛
12(3)
𝑑 𝜋 0 𝜋 0
14(1)
𝑑 𝜋 + 𝜋 −
23(2)
𝑝𝑛 𝜋 + 𝜋 −
30(5)
𝑝𝑛 𝜋 0 𝜋 0
12(2)
𝑝𝑝 𝜋 0 𝜋 −
6(1)
𝑛𝑛 𝜋 0 𝜋 +
𝑁𝑁𝜋
0(<9)
 Eur.Phys.J. A51 (2015) 7, 87

6. Molecule vs Hexaquark

7. 𝑑 ∗ (2380) - Deltaron?
L=0 Δ Δ
see A. Gal, Phys.Lett. B769 (2017) 436 for details

8. Hidden color concept Hexaquark Deltaron
M. Bashkanov, Stanley J. Brodsky, H. Clement Phys.Lett. B727 (2013)
F. Huang et al,  Chin.Phys. C39 (2015) 7,

9. Deltaron vs Hexaquark L=0 Δ Δ ≈33% ≈66% 0.7 fm 0.9 fm 0.9 fm
F. Huang et al,  Chin.Phys. C39 (2015) 7,

10. Deltaron vs Hexaquark ? ≈33% ≈66% ≈10% ≈90% 0.7 fm Δ L=2 Narrow width
Branching ratios
Dalitz plots Δ Δ
≈90%
≈10%
𝑀 𝜋𝜋 , see Nucl.Phys. A958 (2017)
F. Huang et al,  Chin.Phys. C39 (2015) 7,

11. d* internal structure Hexaquark Molecule Diquark dominated
Meson assisted
-dressed 

12. 𝑑 ∗ →𝑁𝑁𝜋 decay Molecular Picture, A. Gal, Phys.Lett. B769 (2017)
D. Arndt 𝑁Δ state has sizable 𝑁𝑁 decay branch: 𝑑 ∗ →𝑁𝑁𝜋 should be seen
Hidden color picture/hexaquark
Yubing Dong, Fei Huang, Pengnian Shen, Zongye Zhang Phys.Lett. B769 (2017) 223
𝑑 ∗ →𝑁𝑁𝜋 decay is tiny

13. 𝑑 ∗ →𝑁𝑁𝜋 decay in experiment
𝑝𝑝→𝑝𝑛 𝜋 +
𝑝𝑝→𝑝𝑝 𝜋 0
Pure isovector (I=1)
𝑝𝑛→𝑝𝑝 𝜋 −
𝑝𝑛→𝑝𝑛 𝜋 0
Mixed (I=1& I=0)
Predominantly isovector
Interested in isoscalar part only
𝜎 𝑁𝑁→𝑁𝑁𝜋 𝐼=0 =3(2 𝜎 𝑝𝑛→𝑝𝑝 𝜋 − − 𝜎 𝑝𝑝→𝑝𝑝 𝜋 0 )
Proton beam
Deuteron target
𝑝𝑑→𝑝𝑝 𝜋 − + p spectator
𝑝𝑑→𝑝𝑝 𝜋 0 + n spectator

14. 𝑑 ∗ →𝑁𝑁𝜋 decay in experiment
𝑁𝑁→𝑁𝑁𝜋 isoscalar cross section
𝜎 𝑁𝑁→𝑁𝑁𝜋 𝐼=0 =3(2 𝜎 𝑝𝑛→𝑝𝑝 𝜋 − − 𝜎 𝑝𝑝→𝑝𝑝 𝜋 0 )
Wasa-at-Cosy arXiv:
Systematical errors!!!!
Same beam
Same detector
Same deuteron target
Two protons in final state measured in the same kinematics
Br( 𝑑 ∗ →𝑁𝑁𝜋)<9% - upper limit
Likely to be close to 0

15. Nuclear matter at high densityp d* n
Mikhail Bashkanov "Dibaryons"

16. The d ∗ (2380) in neutron stars - a new degree of freedom?
I. Vidaña, M. Bashkanov, D.P. Watts, A. Pastore
arXiv: v1

17. 𝑑 ∗ size Transition form factor Charge distribution Internal structure*
d*(2380) d
Transition form factor
Charge distribution
Internal structure

18. d*(2380) in photoproduction?
𝜋 0  p
𝜋 0 d*  d* d d d n
𝛾𝑑→𝑑 𝜋 0 𝜋 0
𝛾𝑑→𝑑 𝜋 0 𝜋 0
Conventional Background M. Egorov, A. Fix, Nucl.Phys. A933 (2015)
𝑑 ∗
M. Guenther Master Thesis, Basel 2015
T. Ishikawa et al.  Phys.Lett. B772 (2017) 398

19. The benchmark measurement
Newly installed Edinburgh polarimeter p  d* d n
Measure polarization of both
proton and neutron !
Mikhail Bashkanov "Dibaryons"

20. Deuteron photodisintegration: beam asymmetry Σ p
Σ~ 𝐽=2 𝐵 𝐽 𝑃 𝐽 2 (𝑐𝑜𝑠Θ) PRC 26 (1982) 2358 d n

21. Deuteron photodisintegration: beam asymmetry Σ p
Σ~ 𝐽=2 𝐵 𝐽 𝑃 𝐽 2 (𝑐𝑜𝑠Θ) PRC 26 (1982) 2358 d n
𝑑 ∗ should be noticeable in 𝑃 6 2 H. Ikeda et al.Nucl. Phys. B 172 (1980) 509

22. Conclusion The very first dibaryon d*(2380) is established
Mass, Width, Quantum numbers
Main decay branches
Structure: Hexaquark vs Molecule?
Medium Modifications?
Neutron Stars?

23. 
*
*
𝑑 ∗ (2380)
Thank you 

24. d*(2380) in photoproduction?
R. Gilman and F. Gross nucl-th/ (2001) d*  p
T. Kamae, T. Fujita Phys. Rev. Lett. 38, Feb 1977, 471 d n
H. Ikeda et al., Phys. Rev. Lett. 42, May 1979, 1321
I(Jp) = 0(3+)
𝐌=𝟐.𝟑𝟖 𝐆𝐞𝐕

25. d*(2380) SU(3) multiplet Jp = 3+  * *  𝑑 ∗ (2380)
𝑀 𝑑 ∗ − 𝑀 Δ + 𝑀 Σ ∗ < 𝑀 𝑑 𝑠 ∗ ≤ 𝑀 Δ + 𝑀 Σ ∗
*
𝑑 𝑠 ∗ (2.53−2.60)
*
𝑑 𝑠𝑠 ∗ (2.68−2.76) 
𝑑 𝑠𝑠𝑠 ∗ (2.82−2.90)

26. Deltaron: the width quest

27. Deltaron: the with quest
2∗Δ(1232) width

28. Deltaron: the with quest
M Δ = 𝑀 𝑑 ∗ − 𝑞 Δ 2
The mass of the bound Δ
in the Deltaron
Δ momentum in the Deltaron
M Δ = 𝑀 𝑑 ∗ 2
only if q Δ =0
q Δ =0 only if the size of the Deltaron is ∞
For R 𝑑 ∗ =0.9𝑓𝑚, Γ 𝑑 ∗ =2 Γ Δ =70 𝑀𝑒𝑉
see A. Gal, Phys.Lett. B769 (2017) 436 for details

29. 𝑁𝑁→𝑁𝑁𝜋 isoscalar cross section
𝜎 𝑁𝑁→𝑁𝑁𝜋 𝐼=0 =3(2 𝜎 𝑝𝑛→𝑝𝑝 𝜋 − − 𝜎 𝑝𝑝→𝑝𝑝 𝜋 0 )
pp→𝑝𝑝 𝜋 0
np→𝑝𝑝 𝜋 −
Complete cancellation of Δ resonance in isoscalar case

30. Beam asymmetry M1 transition ( 𝟏 + ) or E2 transition ( 𝟐 + )  Δ 𝜋 p
E2/M1 ratio for the 𝛾𝑁→Δ
T. Watabe et al. hep-ph
𝐸2 𝑀1 = 1 2 𝑘 𝑀 𝑁 𝑄 𝑧𝑧 𝑁Δ 𝜇 𝑁Δ
R. Beck et al. (MAMI-A2) Phys.Rev. C61 (2000)
Analysis of beam asymmetry
𝐸2 𝑀1 =2.5%

31. 𝑑 ∗ and beam asymmetry Σ 𝑑 ∗ E2 transition ( 𝟐 + )
M3 transition ( 𝟑 + )
E4 transition ( 𝟒 + ) 
𝑑 ∗ p d n
H. Arenhoevel, M. Sanzone “Photodisintegration of the deuteron”

32. Experiment
Target 𝜸 p 𝒏
Θ,𝜙,𝐸 p
𝚯 ′ ,𝝓′
𝛾𝑑→𝑝 𝑛
Polarimeter